Air conditioning control system

ABSTRACT

A control system for an air conditioning or refrigeration apparatus includes a constant pressure regulating valve (automatic expansion valve) between the condenser and the evaporator and a temperature responsive valve between the evaporator and the compressor. Both valves are capable of adjustment to establish: (1) a predetermined pressure (and corresponding temperature) in the evaporator; and (2) a predetermined temperature of the refrigerant in the suction line leading to the compressor. Means are provided for coordinating the setting for both such valves to maintain a certain minimum superheat in the suction gas.

nited States atent Newton Sept. 5, 1972 Primary Examiner-Meyer PerlinAttrneyDonald W. Banner, John W. Butcher and William S. McCurry [72]Inventor: Alwin B. Newton, York, Pa.

[73] Assignee: Borg-Warner Corporation, [57] A S Chicago, 111.

A control system for an air conditioning or refrigera- Filedi 21, 1970tion apparatus includes a constant pressure regulating [21] Appl. No.:99,807 valve (automatic expansion valve) between the condenser and theevaporator and a temperature responsive valve between the evaporator andthe compres- [52] US. Cl. ..62/205, 62/217, 62/225 SOL Both valves arecapable of adjustment to lIIt. establish: a predetennined pressure CO[.[58] Field of Search ..62/205, 210, 217, 222, 225 respondingtemperature) in the evaporator; and (2) a predetermined temperature ofthe refrigerant in the [56] References Cited suction line leading to thecompressor. Means are pro- UNITED STATES PATENTS vided for coordinatingthesetting for both such valves to maintain a certain minimum superheat1n the suc- 3,296,816 1/1967 We11ed ..62/210 tion 2,116,801 /1938Shivers ..62/217 4 Claims, 1 Drawing Figure o 71 68 f o 2:

5 e4 60 52 44 E 4 Q Q 11 Q: 74 6 W ,r-dl

34 2O 56 L 30 I 12 PATENTEDsEr s an INVENTOR AZW/IV 5. NEWTQ/V BY,ZvaQ/Z ATTOR N EV BACKGROUND OF THE INVENTION 1. Field of the InventionAutomatic control of vapor cycle refrigeration or air conditioningsystems in which an automatic expansion valve and a temperatureresponsive suction throttling valve are independently adjustable withmeans for maintaining a minimum superheat to prevent carryover ofliquidin the suction line.

2. Description of Prior Art US. Pat. No. 3,260,064, A. B. Newton, issuedJuly 12, 1966, shows a system utilizing a constant pressure expansiondevice and a suction throttling valve sensing the temperature ofrefrigerant upstream from the throttling valve.

U.S. Pat. No. 3,119,559, J. W. I-leidorn, issued Jan. 28, 1964,describes an automotive air conditioning system provided with anevaporator pressure regulator downstream from the evaporator and athermal expansion valve controlling flow of refrigerant from the highside to the low side of the system.

SUMMARY OF THE INVENTION This invention relates generally to a controlfor refrigeration systems and more particularly to air conditioningapparatus.

In US. Pat. No. 3,119,559, the evaporator pressure regulating valveeffectively prevents the evaporator coil pressure from dropping below apredetermined, non-icing pressure condition, for example, 32 psig. Underlow loads, the evaporator becomes partially flooded, sending slugs ofliquid through to the compressor. This condition sometimes results inbroken compressor valves and other damage.

In US. Pat. No. 3,260,064 (Newton), an improved system is describedwhich includes an adjustable automatic expansion valve and means tocontrol the capacity of the compressor by various techniques, for example, by throttling the suction gas or by unloading one or morecompressor cylinders. In the embodiment using suction gas throttling,the refrigerant temperature is sensed as the gas leaves the evaporatoron the upstream side of the valve.

In the Newton system, if the setting on the automatic expansion valve isadjusted, it is necessary to reset the temperature responsive suctionline valve to assure some minimum superheat in the gas entering thecompressor. For example, assume that a system is using R- 12 refrigerantand that the evaporator pressure is set, by adjustment of the automaticexpansion valve, to 30.07 psig (32F). If 6 of superheat is desired, thesetting on the suction line valve would control the flow to thecompressor so as to maintain 38F because the temperature responsivevalve only reads the temperature component of superheat. If theautomatic expansion valve is then adjusted to higher pressure, say 40.7psig to produce an evaporator coil temperature of 44F the evaporatorcoil would be completely flooded and liquid would flow through thesuction line into the compressor.

In order to avoid this problem, the present invention provides amechanical coordination between the setting of the automatic expansionvalue and the temperature responsive, suction line valve. Such means maytake many forms, but in the preferred embodiment, it may simply be apair of cables interconnecting an adjusting screw on each valve with acontrol dial. The two dials then are provided with interengaging stopmeans so that the respective settings on the automatic expansion valveand the suction line valve cannot be changed to positions which resultin less than the desired minimum superheat.

DESCRIPTION OF THE DRAWING The FIGURE shows a refrigeration or airconditioning system, partly in schematic form, constructed in accordancewith the principles of this invention.

DETAILED DESCRIPTION OF THE INVENTION Referring now to the FIGURE, thereis shown a conventional vapor cycle refrigeration system including acompressor 10, condenser 12, and expansion device 14, evaporator 16, anda temperature responsive, suction line throttling valve 18.

Refrigerant gas is compressed in the compressor 10 and flows throughline 20 to the condenser 12. Liquid refrigerant then flows through line22 to the automatic expansion device 14 which is of a pressureresponsive type, to be described in detail below, maintaining arelatively constant pressure in the evaporator. The low pressure liquidrefrigerant then flows through line 24 to the evaporator, over which airis circulated by means of a blower 26. The refrigerant is evaporatedfrom the inside of the coil and vaporized refrigerant gas flows throughline 28 to the throttling valve 18, and then through line 29 tocompressor 10.

The pressure responsive expansion device 14 is of the type that sensespressure on the downstream side of the valve to maintain a substantiallyconstant pressure in the evaporator. On sensing a drop in pressure, thevalve opens to permit more refrigerant to flow and will close upon arise in pressure. Valve 14 comprises a housing 32 enclosing a diaphragm34 attached to valve member 30, a first spring 36 biasing valve member30 closed, and a second spring 38 biasing it open. The load on spring 38is adjusted by a threaded plug 40 which determines the amount of forcenecessary to open the valve. Pressure on the downstream side of thevalve is applied to diaphragm 34 through line 42, it being understoodthat the pressure could also be transmitted internally of the valve.

The suction line valve 18 comprises a housing 44 having an inlet chamber46 communicating with the evaporator through line 28 and an outletchamber 48 communicating with the suction line of the compressor throughline 29. The housing is provided with a partition 50 separating chambers46 and 48, and having a valve seat 52 which cooperates with valve 54. Atone end of the housing 44 is a valve operating mechanism comprising anoperating bellows 56 connected with a remote thermal responsive bulb 58.The operating mechanism is sealed from chamber 48 by means of abellows-type seal 60 which has a much smaller area than bellows 56. Thestem 62 of valve 54 is attached to the operating bellows which expandsand contracts in response to temperature sensed by bulb 58. Remote bulb58 may be located either on the suction line 29 downstream from thevalve, or in line 28 connecting the evaporator and the valve. In theFIGURE, the bulb is shown as being located in contact with line 28. The

force required to close the valve 54 i.e., the control point, isadjusted by the compression on spring 64, said spring being interposedbetween the operating bellows and an adjusting screw 66.

In accordance with the invention, the settings of the automaticexpansion device 14 and the suction line valve 18 are mechanicallycoordinated to maintain some minimum degree of superheat. This may beaccomplished in a relatively simple manner by interconnecting theadjustment screw 40 on valve 14 with an operating lever 68 via a torquetransmitting cable 70; and adjusting screw 66 is connected to lever 72by cable 74. For convenience, a common dial 7! may be used to correlatethe position of levers 68 and 72 with the evaporator temperature andsuperheat setting, respectively.

In order to assure that some minimum degree of superheat is presentregardless of the settings on the respective levers, a lug 76 may beattached to one or the other of such levers, so that this providesinterengaging stop means for preventing the position of lever 72 to bepushed beyond the setting of lever 68. For example, any attempt to movelever 72 counter clockwise (reducing superheat) will result inengagement of lever 68 to resposition it to a lower setting. Conversely,movement of lever 68 in a clockwise direction to obtain a higherevaporator pressure, will automatically move the suction line valve to acorresponding higher superheat setting.

While the invention has been described in connection with a certainspecific embodiment thereof, it is to be understood that this is by wayof illustration and not by way of limitation; and the scope of theappended claims should be construed as broadly as the prior art willpermit.

What is claimed is:

l. Refrigeration apparatus comprising: a compressor, a condenser, and anevaporator connected in a closed circuit, vapor cycle system throughwhich a refrigerant is circulated; a constant pressure expansion deviceoperatively connected between said condenser and said evaporator tomaintain a predetermined pressure (and corresponding temperature) ofrefrigerant in said evaporator; temperature responsive valve meansoperatively connected between said evaporator and said compressor tocontrol the flow of refrigerant therebetween, and maintain apredetermined superheat of the refrigerant leaving said evaporator;first adjusting means for adjusting the control point of said constantpressure expansion device; second adjusting means for independentlyadjusting the control point of said valve means; and means formechanically interconnecting said first and second adjusting means tomaintain a predetermined minimum temperature differential between thecontrol point of said expansion device and the control point of saidtemperature responsive valve means.

2. Apparatus as defined in claim 1 wherein said first adjusting meansincludes a remotely located lever for changing the control point of saidconstant pressure expansion device, and said second adjusting meansinsion device is adju ted to a setting which would result in atemperature d1 ferential lower than said predetermined minimum.

3. In a refrigeration apparatus of the type including a compressor, acondenser, and an evaporator connnected in a closed circuit, vapor cyclesystem through which a refrigerant is circulated; a constant pressureexpansion device operatively connected between said condenser and saidevaporator to maintain a predetermined pressure (and correspondingtemperature) of refrigerant in said evaporator; temperature responsivevalve means operatively connected between said evaporator and saidcompressor to control the flow of refrigerant therebetween and maintaina predetermined superheat of the refrigerant leaving said evaporator;the improvement comprising first adjusting means for adjusting thecontrol point of said constant pressure expansion device; secondadjusting means for independently adjusting the control point of saidvalve means; and means for mechanically interconnecting said first andsecond adjusting means to maintain a predetermined minimum temperaturedifferential between the control point of said expansion device and saidtemperature responsive valve means.

4. Refrigeration apparatus comprising: a compressor, a condenser, and anevaporator connected in a closed circuit, vapor cycle system throughwhich a refrigerant is circulated; a constant pressure expansion deviceoperatively connected between said condenser and said evaporator tomaintain a predetermined pressure (and corresponding temperature) ofrefrigerant in said evaporator, said expansion device including apressure responsive element actuating a valve, said valve closing upon arise in evaporator pressure; temperature responsive valve meansoperatively connected between said evaporator and said compressor tocontrol the flow of refrigerant therebetween and maintain apredetermined superheat of the refrigerant entering said compressor,said temperature responsive valve means having a temperature responsiveelement opening said valve means upon a temperature rise; firstresilient means opposing the valve opening force of said temperatureresponsive element, first adjusting means for adjusting the compressiveforce on said first resilient means; second resilient means opposing theclosing force of said pressure responsive element, and second adjustingmeans for adjusting the compressive force on said second resilientmeans; first and second remotely located levers operatively connectedrespectively to said first and second adjusting means; a lug attached toone of said levers adapted to engage the other of said levers after apredetermined rotation in a direction toward the same, the interengagingof said lug with said lever being adapted to prevent the setting of theconstant pressure expansion device to produce a temperature lower than apredetermined temperature difference between the refrigerant in saidevaporator and the refrigerant passing through said valve means.

1. Refrigeration apparatus comprising: a compressor, a condenser, and anevaporator connected in a closed circuit, vapor cycle system throughwhich a refrigerant is circulated; a constant pressure expansion deviceoperatively connected between said condenser and said evaporator tomaintain a predetermined pressure (and corresponding temperature) ofrefrigerant in said evaporator; temperature responsive valve meansoperatively connected between said evaporator and said compressor tocontrol the flow of refrigerant therebetween, and maintain apredetermined superheat of the refrigerant leaving said evaporator;first adjusting means for adjusting the control point of said constantpressure expansion device; second adjusting means for independentlyadjusting the control point of said valve means; and means formechanically interconnecting said first and second adjusting means tomaintain a predetermined minimum temperature differential between thecontrol point of said expansion device and the control point of saidtemperature responsive valve means.
 2. Apparatus as defined in claim 1wherein said first adjusting means includes a remotely located lever forchanging the control point of said constant pressure expansion device,and said second adjusting means includes an adjacent lever, andinterengaging stop means on one of said levers adapted to reset thecontrol point of said temperature responsive valve when said expansiondevice is adjusted to a setting which would result in a temperaturedifferential lower than said predetermined minimum.
 3. In arefrigeration apparatus of the type including a compressor, a condenser,and an evaporator connnected in a closed circuit, vapor cycle systemthrough which a refrigerant is circulated; a constant pressure expansiondevice operatively connected between said condenser and said evaporatorto maintain a predetermined pressure (and corresponding temperature) ofrefrigerant in said evaporator; temperature responsive valve meansoperatively connected between said evaporator and said compressor tocontrol the flow of refrigerant therebetween and maintain apredetermined superheat of the refrigerant leaving said evaporator; theimprovement comprising first adjusting means for adjusting the controlpoint of said constant pressure expansion device; second adjusting meansfor independently adjusting the control point of said valve means; andmeans for mechanically interconnecting said first and second adjustingmeans to maintain a predetermined minimum temperature differentialbetween the control point of said expansion device and said temperatureresponsive valve means.
 4. Refrigeration apparatus comprising: acompressor, a coNdenser, and an evaporator connected in a closedcircuit, vapor cycle system through which a refrigerant is circulated; aconstant pressure expansion device operatively connected between saidcondenser and said evaporator to maintain a predetermined pressure (andcorresponding temperature) of refrigerant in said evaporator, saidexpansion device including a pressure responsive element actuating avalve, said valve closing upon a rise in evaporator pressure;temperature responsive valve means operatively connected between saidevaporator and said compressor to control the flow of refrigeranttherebetween and maintain a predetermined superheat of the refrigerantentering said compressor, said temperature responsive valve means havinga temperature responsive element opening said valve means upon atemperature rise; first resilient means opposing the valve opening forceof said temperature responsive element, first adjusting means foradjusting the compressive force on said first resilient means; secondresilient means opposing the closing force of said pressure responsiveelement, and second adjusting means for adjusting the compressive forceon said second resilient means; first and second remotely located leversoperatively connected respectively to said first and second adjustingmeans; a lug attached to one of said levers adapted to engage the otherof said levers after a predetermined rotation in a direction toward thesame, the interengaging of said lug with said lever being adapted toprevent the setting of the constant pressure expansion device to producea temperature lower than a predetermined temperature difference betweenthe refrigerant in said evaporator and the refrigerant passing throughsaid valve means.